objective-c - iOS:如何将 UIViewAnimationCurve 转换为 UIViewAnimationOptions？

Question

UIKeyboardAnimationCurveUserInfoKey有一个 UIViewAnimationCurve值(value)。怎么转换成对应的UIViewAnimationOptions与 options 一起使用的值+[UIView animateWithDuration:delay:options:animations:completion:]的论据?

// UIView.h

typedef enum {
    UIViewAnimationCurveEaseInOut,         // slow at beginning and end
    UIViewAnimationCurveEaseIn,            // slow at beginning
    UIViewAnimationCurveEaseOut,           // slow at end
    UIViewAnimationCurveLinear
} UIViewAnimationCurve;

// ...

enum {
    // ...
    UIViewAnimationOptionCurveEaseInOut            = 0 << 16, // default
    UIViewAnimationOptionCurveEaseIn               = 1 << 16,
    UIViewAnimationOptionCurveEaseOut              = 2 << 16,
    UIViewAnimationOptionCurveLinear               = 3 << 16,
    // ...
};
typedef NSUInteger UIViewAnimationOptions;

显然，我可以使用 switch 创建一个简单的类别方法。声明，像这样:

// UIView+AnimationOptionsWithCurve.h

@interface UIView (AnimationOptionsWithCurve)
@end

// UIView+AnimationOptionsWithCurve.m

@implementation UIView (AnimationOptionsWithCurve)

+ (UIViewAnimationOptions)animationOptionsWithCurve:(UIViewAnimationCurve)curve {
    switch (curve) {
        case UIViewAnimationCurveEaseInOut:
            return UIViewAnimationOptionCurveEaseInOut;
        case UIViewAnimationCurveEaseIn:
            return UIViewAnimationOptionCurveEaseIn;
        case UIViewAnimationCurveEaseOut:
            return UIViewAnimationOptionCurveEaseOut;
        case UIViewAnimationCurveLinear:
            return UIViewAnimationOptionCurveLinear;
    }
}

@end

但是，有没有更简单/更好的方法？

Answer 1

您建议的类别方法是执行此操作的“正确”方法 - 您不一定能保证这些常量保持其值。但是，从查看它们的定义方式来看，您似乎可以这样做

animationOption = animationCurve << 16;

...如果编译器想提示的话，可能会先转换为 NSUInteger，然后再转换为 UIViewAnimationOptions。